Safety element to permanently assure the electric reliability of pulse transmitting leads utilized in cardiac pacemakers for the electric stimulation of the heart

Abstract

Safety element intended to assure in time the electric reliability of pulse transmitting leads, comprised in apparatus for the electric stimulation of the heart (pacemaker) and consisting of a main metallic coil of tubular structure delimiting an inner bore, covered by an insulating sheath, which safety element comprises a flexible lead formed by one or more wires coiled in tight turns or intertwined and provided with a rounded head for making it easier the introduction of the safety element in the bore of the main metal coil of the pulse transmitting lead.

We claim: 
     
       1. In a heart stimulation apparatus of the type comprising a pacemaker, received in a subcutaneous pocket formed in the patient's chest, for generating stimulation pulses and a pulse transmitting lead (12) forwarding said pulses to the patient's heart, provided with a pin-jack (11) for connection to the pacemaker and a distal end (18) to be fixed to the endocardium of the right ventricle of said heart (HT) for transmitting thereto said stimulation pulses, wherein said pulse transmitting lead (12) has a coaxial, tubular structure consisting of an outer sheath (14) and an inner main coil (13) formed by one or more wires helically wound in closely tight turns, delimiting an inner bore (15) which bore, during first implantation of said pulse transmitting lead (12) in the patient's body, accommodates a thin, solid wire, mandrel (MN) that provides said pulse transmitting lead (12) the rigidity necessary to allow the pulse transmitting lead to be pushed from said subcutaneous pocket to the patient's heart (HT), wherein said distal end is adapted to be fixed to the heart's right ventricle, said mandrel (MN) being removed when said implantation is completed, the improvement comprising: a safety element (16, 116) insertable at the time of the necessary replacement of said pacemaker, comprising one or more electrically conductive very flexible wires wound to form a cylindrical body and sized to be fitted in said inner bore (15) of said main coil (13) for substantially continuous electrical contact with the inner surface of the main coil from the pin jack to the distal end of the pulse transmitting lead, capable of permanently assuring the electric continuity of said pulse transmittal lead even if cracks or micro-fractures have occurred therein. 
     
     
       2. The improved heart stimulation apparatus, wherein the one or more wires of the safety element are helically wound in tight turns to form a coil (16). 
     
     
       3. The improved heart stimulation apparatus of claim 1 wherein the one or more wires of the safety element comprise a plurality of very thin wires intertwined to form a flexible braid. 
     
     
       4. The improved heart stimulation apparatus of claim 1, wherein the safety element is provided with a rounded head (19, 119) to facilitate the introduction of said element (16, 116) in the bore (15) of said main coil (13).